Method of extracting broken drills and the like



Patented Oct. 28, 1947 METHOD OF EXTRACTING BROKEN DRILLS AND THE LIKE 1 N iels A. Sorensen,

Cleveland Heights, Ohio;

Phillips N. Sorensen, administrator of said 1 Niels A. Sorensen, deceased; assignor, by mesne assignments, to Phillips N. Sorensen and Richard L. Garber, Cleveland, Oho

Application March 1, 1944, Serial No. 524,650

5 Claims. (Gl. 29-148) The presentI invention relate's to theextraction of tool parts, such as drill bits, reamers, taps and plug gaug'es, from holes in metal in which such tools have become broken off, or -tightly jammed' or wedged. Quite freuently, the inability to remove such tool parts by expedients heretofore known has resulted in the rendering useless and scrapping of the entire metal part that is being machined.

Inasmuch as cutting tools, such as drills, reamers, taps, etc., are-harder and/or tougher than the metal stock of the metal part which is being machined, it is not feasible to attempt to remove the broken or jammed tool part by drilling it out of the hole, or by attempting to remove it with a mechanical gripping device such as an extracting screw.

I have discovered that such tool parts can be 2 .i those on the order of I of an inch di'ameter, can be eiectively blown free by my extraction method. To the accomplishment of the foregoing and related ends, said invention, then,l consists of the means hereinafter fully described and particularly pointed out'in the clai'ms,V the annexed drawing and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various Ways in which the principle of theinvention may be used.

' In said annexed drawing:

. Fig. 2 shows a drill broken oflf in line with the top of the hole, similarly prepared efliciently, quickly and very inexpensively removed from the hole in which they are jammed or broken off by means of applying a charge of high'velocity'explosive, having a velocity of combustion rate on the order of 5,000 to 20,000, ft. per second.b Dynamite is alcommerciallyavailable high explosive well suited to "the practice of the processof my invention. Other high velocity explosives which-may bve'used are blasting gelatin, nitroglycerin, nitrocellulose, ammonium nitrate. nitrostarch and liquid oxygen explosives' top or outermost end of the broken or jammed tool part, which results in a blowing or blasting of the tool part back out of the hole. Ordinarily it would be expected that the detonation of an Fig. 3 illustrates the method of removinga tap;

and m l v Fig. 4 illustrates the method of removing a plug gauge.

Referring to Fig. 1, the broken twist drill part I i is shown broken off and jammed in the hole 2.

ythe top of the hole 2.

The top or outermost end 3 of the drill I is below In this case, a charge of dynamite is placed on the outer end 3 of the broken drill, in the form Vof the layer 4. The amount'of the charge of dyamite is relatively small, and even in the case of extracting drills or other tool parts as large as 11/1 in. in diameter, not more than a thimbleful of dynamite is necessary. As a general rule, a layer of dynamite 4 having a thickness or depth not over IA of the diameterof the hole 2 is the appropriate amount to be used.. A detonating cap 5 is then inserted in the dynamite layer 4, with the fuse 6 connected thereto. Upon lighting the fuse 6 and detonatexplosive charge on the top of the tool part would force itdeeper and tighter into the hole, but my invention is based upon the discovery that just the opposite result ensues,

My invention possesses the further advantage in that on harm or damage is done to the metal the case of the extraction of large core drills surrounding the hole from which the broken or jammed tool part is removed. Not even local stresses or strains are set up in the metal by my extracting process, as has been proven by a great many tests and inspections, such as by magnafluxtesting. fr A further object and advantage of my invening the charge of dynamite 4, the broken drill I is blown out of the hole, accompanied by the ringing noise "of metal strikirig, metal.

In some instances, it is necessary to repeat the process, viz., to insert anothercharge of explosive and again detonate lt, to remove all of the broken tool part. This is most likely to occur in which become fractured and hence must be removed piece by piece by repeated explosive charges.

Where a tool part, such as the drill 1, is broken off substantially at or above the top of the hole 8, as indicated at 9, the explosive charge is placed on top of the tool part, as indlcated at Ill. A

non is that reiatively sman cjameter tooisi, e.,\5 mound of plastic material II. such as putty 017` clay, is built around the top of the charge Ill, the4 cated at IS, out of the hole I 6, the procedure is the same as heretofore described, viz., byplacing a charge II of dynamite on the outer end of the tap v andthen detonating the same. In this case,`however, the tap, being blown out of the hole, will strip off a section of threads l'8. However, strange to relate, only. one portion'of the entire periphery of the threads 18 will be cut off. This portion of cutI off threads corresponds in width or extent to one of the lands between the fiutes IS of the tap IS. After removal of the broken tap part IS, the hole IG can then be re-tapped to a slightly oversized diameter of thread.

Although I do not wish to linit myself to any particular scientific theory of operation of my method, it is believe'd that the force of the blast, or the explosive gases from the charge travel down between the fiutes of the tool to the bottom of the hole and there the pressure reverses itself to drive the tool back out of the hole.

In the case of a tool or tool part which does not have any channels, gashes or flutes extending from its outer to its inner end, such as the plug gaugev 20 shown in Fig. 4, a small hole 2! is first drilled through the length of the plug gauge, before the explosive charge 22 is placed on top of the tool part 20 and'detonated.

In cases where the outer or exposed end of the broken tool part is below the surface of the hole, it is recommended that a wire rod or probe be first used to determine the position of the end of the drlll below the top of the hole, so that the operator will be able to make sure that he places the explosive charge far enough into the hole and upon the exposed or outer end of the broken tool Part.

My above-described method is particularly suited for removing toolparts from deep drilled holes, which heretofore have presented the most serious problem in the removal of broken drills and the like. My invention thus results in the saving of metal parts and workpieces which would otherwise have to be scrapped, representing an important and outstanding saving not only in labor, but also material.

Other modes of applying the principle of my invention may be employed instead of the one tools, such as drills and the like, from holes having a closed inner end in metal parts, comprising providing apassagewayfor gases to the inner end of such hole, placng a small charge of high velocity explosive on the'outermost end of the tool part to be extracted, and then detonating such charge and blowing the tool part back out of the hole.

2. The method of extracting fiuted tools such `as drills, reamers and taps from holes having a closed inner end in metal parts, comprising providing a passageway for gases to the inner end of such hole, placing a small charge of dynamitel on the outermost end of the tool to be extracted, and-then detonating such charge and blowing the tool back out of the hole.

3. The method of extracting broken parts of tools, such as drills and the like, which are broken off at or beyond the outer end of a hole having a closed inner end in a metal part, comprising providing a passageway for gases to the inner end of such hole, placing a small charge of dynamite on the topiof the broken'tool, placing a, mound of inert, plastic material on top of the dynamite and surrounding the outer end of the hole, and then detonating such charge and blowing the tool part out of the hole.

4. The method of extracting cylindrical tools such as plug gauges and the like from holes having a closed inner end in metal parts, comprising thesteps of drilling a passageway for gases to such closed inner end through the tool part to be removed, placing a small charge of dynamitev onvthe outermost end of thetool part, and then detonating the charge and blowing the tool out of the hole.

5. The method of extraeting fiuted tools such as drills, reamers and taps from holes having a closed inner end in metalparts, comprsing providing a passageway for gases to the inner end of such hole, placing a, small charge of dynamite in a layer having a depth not over 1/3 the diameter of the hole? on the outermost end of the tool to be extracted, and then detonating such charge and blowing the tool out of the hole.

NIELS A. SORENSEN.

REFEREN CES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,367,206 Davis Jan. 16, 1945 2,331,16'7 Brecht Oct. 5, 1943 OTHER REFERENCES 

